Aerospace and Electronic Systems - March 2019 - 48

ARIES: An Autonomous Controller For Multirobot Cooperation

Figure 8.
Mandatory configurations and basic work flows to deploy the cooperation in ARIES. The cooperation among two T-REX agents is carried
out via observations and goals. The normal black lines represent the communication flow of observations and goals. The dashed black lines
represent waiting states in the coordination among different agents. The red dashed lines represent different failure states that a reactor
communicate to other reactor.

T-REX OVERVIEW"). These values are a matter of
design of the user. Then, attending to the T-REX notation,
its dispatching window HD can be stated as (1).
At the middle level, the cooperative layer is formed
by the COOP Reactor, a T-REX reactor whose objective is to carry out the cooperation with the Followers.
Figure 8 shows that the COOP Reactor deploys a TCP/
IP server to connect with every Follower and it declares
every state variable of every Follower as internal. Then,
when a new sequence of tokens has been planned, the
Planner Reactor sends the Follower's goals to the
COOP Reactor (A.1 in Figure 8). Thus, the COOP
Reactor forwards the goals to the COOP Reactor of the
corresponding Follower (A.2 in Figure 8) for execution
and then it waits (Leader Waiting in Figure 8) for the
reception of the Follower observation (A.5 in Figure 8).
Then, it reports this observation to the Planner Reactor
(A.6 in Figure 8). Hence, this layer manages the communication failure, where the Leader waits for any
heartbeat signal from any Follower. If a time threshold
(defined by the user) is reached and none Follower had
sent the heartbeat signal, this layer reports the wrong
state to the Planner Reactor to perform replanning.
At the bottom level, the executive layer is formed by
the GER, an execution module designed to be easy
adaptable to any robotic domain. Figure 8 shows that the
GER declares every state variable of the Leader Agent
as internal. Its role is to dispatch the tokens, over its
internal state variables, to the functional layer of the
robotic platform. Then, when the goal has been reached,
it sends the observation to the Planner Reactor (B.2 in
Figure 8). Therefore, it provides an interface between
the Planner Reactor and the functional layer without
48

creating knowledge dependencies between them. Also, it
has the capability to monitor the tokens execution. Thus,
this layer manages the unachieved goal failure, in which
the GER sets a fail-safe mode. In this mode, it tries to
repair the error as soon as possible by isolating the event
from the whole system and triggering a reactive rule to
solve it in a short time. The fail-safe mode requires
a configuration file where the user has to define the
reactive rule to trigger for every unachieved goal. For
instance, if the Leader's camera cannot take a picture,
the user can set a reactive rule to reboot the camera that
might solve the issue. Thus, it avoids to report to the
Planner Reactor the failure to avoid collateral effects.
However, if the failure persists after executing all possible recovering rules (Leader Failure in Figure 8), the
GER notifies to the Planner Reactor, asking for a replanning that may affect the whole mission.
The GER is considered as a reactive reactor, where the
latency ¼ 0 and the look-ahead p ¼ 1 within the timing
model of the T-REX application. Then, its dispatching
window HD can be defined as follows:
HD ¼ ½t þ ; t þ þ p
¼ ½t; t þ 1 ! ¼ 0; p ¼ 1:

(2)

FOLLOWER AGENT
The Follower Agent is a T-REX agent, which provides a
wide range of functional capabilities in order to accomplish complex cooperative missions. These capabilities
depend on the deployed robotic system. It is made up of
three T-REX reactors, each one placed in a different layer

IEEE A&E SYSTEMS MAGAZINE

MARCH 2019

Aerospace and Electronic Systems - March 2019

Table of Contents for the Digital Edition of Aerospace and Electronic Systems - March 2019